In current time division multiplex/frequency division duplex (TDD/FDD) network radio equipment, such as a base transceiver station (BTS), a mismatch on the antenna transmission line causes transmission loss and standing waves. This mismatch can be expressed in terms of a voltage standing wave ratio (VSWR) and a distance to the fault and serves as input to start on-site maintenance actions.
In general, VSWR may be determined from the voltage measured along a transmission line leading to an antenna. Thereby, VSWR is the ratio of the maximum amplitude of a standing wave to the minimum amplitude of a standing wave. In case an antenna is not matched to the transmitter, power is reflected, which causes a reflected voltage wave, creating standing waves along the transmission line.
However, the on-site location of a VSWR fault requires disconnecting of the antenna line from the base transceiver station (BTS) and connecting of external measurement equipment to the antenna line and/or visual inspection.
Consequently, an unknown location of the fault requires expenditure of time to detect. Further, appropriate measurement equipment to detect the fault requires investments.